Men in the age group still have more heart disease, but the gender differences seem to be narrowing. Researchers suspect increases in obesity are to blame for the 'ominous trend.'

Middle-aged men still have higher rates of heart attacks and heart disease than middle-aged women, but those gender differences appear to be narrowing, according to a study published Monday.

The findings follow earlier research, published in a 2007 issue of the journal Neurology, establishing that stroke prevalence among women ages 45 to 54 was double that of men of the same age. Together, the findings suggest "an ominous trend in cardiovascular health among midlife women," said the lead author of both studies, Dr. Amytis Towfighi, an assistant professor of neurology at the University of Southern California.

Women have been thought to be largely protected from heart attacks and stroke prior to menopause due to hormonal influences. But the rising rate of obesity, which is higher in middle-aged women than middle-aged men, could undermine that natural benefit.

"People didn't think that women in that age group were at high risk for heart disease and stroke," she said. "But I suspect that with growing rates of obesity, women aren't as protected as much as they have been in the past."

The new study, published in the Archives of Internal Medicine, examined national survey data from 1988 through 1994 and from 1999 through 2004. More than 4,000 men and women, ages 35 to 54, participated. Researchers looked at heart attack rates as well as scores from a measure used to predict the risk of a having a heart attack in 10 years. This risk-assessment tool includes factors such as age, cholesterol levels, blood pressure and smoking history.

In both time periods, men had more heart attacks than women. But the rates of men improved from 2.5% in the earlier period to 2.2% in the second time frame; women's rates increased from 0.7% to 1%.

Men's cardiovascular risk factors improved or remained stable over the two study periods, whereas the only risk factor that improved in women was high-density lipoprotein levels. This suggests that precursors to heart disease, such as high blood pressure and high cholesterol, are not assessed or treated as aggressively in women, said Towfighi, also chairwoman of the neurology department at Rancho Los Amigos National Rehabilitation Center.

"There have been several studies that have found women have their risk factors checked less frequently than men," she said. "When they are checked, women are less likely to receive medication than men. And when they receive medication, their symptoms are not as controlled as much as men."

However, a second paper published in the same journal reveals that some strides are being made in treating women's cardiovascular health. That study found survival rates following a heart attack improved in both men and women between 1994 and 2006, with the biggest improvements seen in women.

Researchers led by Dr. Viola Vaccarino of Emory School of Medicine, looked at in-hospital death rates following heart attacks in 916,380 patients. Women younger than 55 had a 52.9% reduction in the risk of death over the time period, whereas men of the same age had a 33.3% reduction.

The two studies looked at somewhat different risk factors and different time periods, which could account for the more positive findings of the study on death rates, Towfighi said. "The second study is encouraging. But although mortality is improving in recent years, women are having more heart attacks," she said.